clang build fails

[arcan1s]

As of 2015-04-15 and for a few weeks previously, this package fails to
build with CXX=clang++. Works fine with g++ and "ccache g++". Errors
are like this:

/tmp/yaourt-tmp-justin/aur-plasma5-applet-netctl-gui/src/netctl-gui/netctlgui/include/netctlgui/netctlinteract.h:290:36:
error: use of undeclared identifier 'nullptr'
    NetctlProfile *netctlProfile = nullptr;